In recent years, interconnects formed in semiconductor devices have been increasingly scaled down along with an increase in the degree of integration (density) of semiconductor devices. A damascene method has been known as technology capable of scaling down interconnects. In the damascene method, grooves or the like formed in an insulating layer are filled with an interconnect material, and an unnecessary interconnect material deposited in an area other than the grooves is removed by chemical mechanical polishing to form desired interconnects. When using copper or a copper alloy as an interconnect material, a high-strength, high-dielectric-constant insulating layer (barrier layer) is generally formed of tantalum, tantalum nitride, titanium nitride, or the like at the interface between copper or a copper alloy and the insulating material in order to prevent migration of copper atoms into the insulating layer.
When using the damascene method in the production of semiconductor devices using copper or a copper alloy as an interconnect material, chemical mechanical polishing is performed in various ways. As the chemical mechanical polishing method, two-stage chemical mechanical polishing may be performed which includes a first polishing step of mainly removing copper or a copper alloy and a second polishing step of mainly removing the barrier layer.
Since interconnects formed in semiconductor devices have been scaled down, the first polishing step is required to polish copper at a rate of 800 nm/min substantially without polishing the barrier layer and control copper dishing to 20 nm or less. When using a low-dielectric-constant material (low-k material) for an insulating layer, since delamination or layer breakage occurs when friction occurs to a large extent during polishing, it is difficult to apply a chemical mechanical polishing aqueous dispersion which causes friction to occur to a large extent during polishing.
The second polishing step is required to polish the polishing target surface with low friction in the same manner as in the first polishing step to improve the hydrophilicity of the polishing target surface and an abrasive cloth, thereby reducing copper scratches, copper corrosion, and insulating layer scratches while reducing copper dishing and insulating layer erosion.
In order to satisfy the above-mentioned demands for the first polishing step and the second polishing step, various chemical mechanical polishing aqueous dispersions using a water-soluble polymer such as polyvinylpyrrolidone have been proposed.
For example, JP-A-2003-282494 discloses a chemical mechanical polishing aqueous dispersion containing a polyoxo acid or its salt, a water-soluble polymer, and water. JP-A-2003-282494 describes that the chemical mechanical polishing aqueous dispersion reduces defects (e.g., scratches and dishing) of the polishing target surface.
JP-A-2002-270549 discloses adding polyvinylpyrrolidone as a dispersant for abrasive grains contained in a chemical mechanical polishing aqueous dispersion.
JP-A-2002-517593 discloses a chemical mechanical polishing aqueous dispersion containing water, abrasive grains, an oxidizing agent, and an organic polymer. JP-A-2002-517593 describes that the organic polymer may be polyvinylpyrrolidone. JP-A-2002-517593 describes that the chemical mechanical polishing aqueous dispersion reduces the polishing rate using the abrasive grains.
Specifically, the above-mentioned patent documents add a water-soluble polymer such as polyvinylpyrrolidone to the chemical mechanical polishing aqueous dispersion aimed at causing the water-soluble polymer to adhere to the abrasive grains or the polishing target surface to improve the dispersibility of the abrasive grains or reduce the polishing rate for the polishing target surface.
When using such a water-soluble polymer, the dispersibility of the abrasive grains can be improved, and the polishing rate for the polishing target surface can be reduced. On the other hand, since the water-soluble polymer also adheres to the polishing target area, the polishing rate decreases to a large extent, whereby incomplete copper removal or the like occurs.